Ultrasonic surgical instruments are finding increasingly widespread applications in surgical procedures by virtue of the unique performance characteristics of such instruments. Depending upon specific instrument configurations and operational parameters, ultrasonic surgical instruments can provide substantially simultaneous cutting of tissue and hemostasis by coagulation, desirably minimizing patient trauma. The cutting action is typically effected by an end-effector at the distal end of the instrument, with the end-effector transmitting ultrasonic energy to tissue brought into contact therewith. Ultrasonic instruments of this nature can be configured for open surgical use, or laparoscopic or endoscopic surgical procedures.
Ultrasonic surgical instruments have been developed that include a clamp mechanism to press tissue against the end-effector of the instrument in order to couple ultrasonic energy to the tissue of a patient. Such an arrangement (sometimes referred to as an ultrasonic transactor) is disclosed in U.S. Pat. No. 5,322,055, hereby incorporated by reference.
As will be appreciated, effecting the desired coupling of ultrasonic energy to the tissue of a patient requires that the clamp mechanism of an ultrasonic instrument be configured to exert sufficient compression clamping force between the clamp arm and the associated end-effector. While providing suitable clamp mechanisms in relatively large ultrasonic surgical instruments has been achieved in the past, presently preferred instruments are relatively thin, and a relatively small cross-section. By way of example, current instruments have a diameter less than about 6 mm, thus limiting the "envelope" within which a clamping mechanism must be positioned. As will be recognized, the clamping force is a function of the moment arm which is created about the pivot axis of the clamp arm of the clamping mechanism, with the advent of such relatively small instruments limiting the available space for creating the desired mechanical pivoting force. Additionally, it is ordinarily preferred to provide an end-effector dimensioned as large as possible, within the confines of the relatively small instrument, since this desirably abates excessive heating of the end-effector, and promotes efficient ultrasonic cutting and coagulation.
The present invention is particularly directed to an ultrasonic clamp coagulator apparatus which includes an improved clamping mechanism which has been specifically configured to convert longitudinal motion into a pivotal clamping motion for creating the desired clamping force in a surgical instrument having a relatively small cross-section.